Nonnumerical rotary homing type switch



R. TAYLOR ETAL NON-NUMERICAL ROTARY HOMING TYPE SWITCH Jul 22, 1947.

Filed Dec. 11, 1944 5 Sheets-Sheet 1 INVENTORS 'REGINALD TAYLOR GEORGEYTHOMAS BAKER July 22, 1947. R. TAYLOR ET AL 2,424,519

NON-NUMERICAL ROTARY H OMING TYPE SWITCH I Fild Dec. 11 1944 5 Sheets-Sheet 2.

INVENTORS REGINALD TAYLOR GEORGE-THOMAS BAKER BY%ZM AT TORN EY July 22, 1947. RiTA'YLOR ETAL NON-NUMERICAL ROTARY HOMING TYPE SWITCH Filed Dec. 11 1944 5 Sheets-Sheet 3 I v INVENTORS REGINALD TAYLOR GEORGE THOMAS BAKER ATTORNEY Patented July 22, 1947 NONNUMERICAL ROTARY HOMING TYPE swrrcn Reginald Taylorv and GeorgeThomas BakenLiverpool, EnglamL. assig trio Laboratories Inc.,

tion of Delaware nors to Automatic Elec- Chicago, Ill., a corpora- Application December 11, 1944, Serial No. 567,551 InGreatBritain February 1, 1944..

Claims. (Cl. 179-18) The present invention relates to telephone'or like systems and is more particularly concerned with subscribers line circuits of the type incorporating a forwardly hunting switch for connecting the subscribers line with a first numerical switch which will subsequently respond to the first dialled digit. The general object of the invention is to provide a subscribers line circuit suitable for satisfactory operation over very long lines. and permitting toll breakdown facilities with the employmentof only two relays of standard type with non-marginal operation.

According to one feature of the invention, in a subscriber's line circuit comprising a line relay and a cut-off relay and a non-numerical switch of the rotary homing type giving access to a group of first numerical switches, during out: going calls the application of potential to the guarding conductor extending. to the final. selectors over which incoming. calls. are. completed is made by-way of the low resistance winding of the cut-off relay and a wiper of the switchin ofi-normal position in order to enable .therelay to bereleased by the application of direct guarding potential from a final selector. V

According to anotherfeature of the invention, in a subscribers line circuit comprising. a. line relay and a cut-off relay and a non-numerical switch of the rotary homing typegiving access to a group of first numerical switches, the. guard-, ing. conductor extending to the final selectors overwhich incoming calls are completed is com nected to an auxiliary wiper of the rotary switch and the contact engaged by this wiper in normal position is connected to one terminal of the cut-off relay which is also arranged to be connected to the guarding and holding wiper of. the switch throughout an outgoing connectionwhile the contacts engagedby the auxiliary wiper when in off-normal position are connected to the other terminal of the cut-off relay so that the connection of the same potential to the guarding 0on ductor in the. final selector will produce-operation or release of the cut-off relayaccording as the switch is. in normal or off-normal position.

The invention will be better. understood from the following description of one method .of carrying it into eifect whichshould be taken in .con junction with the accompanying drawings comprising Figs. 1-3. Of these Fig. 1 shows details of asubscribers line. circuit employinga so-called uniselector embodying the invention, while Figs. 2 and 3 when arranged side by sideshow the circuit of a modified numerical switchaof the 200-outlet type arranged for operationxas. a first selector and assumed to be directly accessible from the'uniselector of Fig. 1.

Considering first the operation of the uniselectorl of'Fig'. 1 on an outgoing call, when the line SL.is looped by the subscriber removing his receiver, relay L is operated from earth at contacts K4' over. wiper DI of the uniselector in normal position, subscribers: loop, contacts Kl, common lead In to battery by way of one of the alternative connections the purpose of which will be described subsequently. Relay L thereupon energises and. at contacts Ll completes a locking circuit for itself independently of wiper DI, and at contacts L2 and L3 completes a circuit over wiper D3 in normal position for the uniselector driving magnet DM, by way of. its interrupter contacts DMC. Earth supplied by contacts L3 also extends to one side of the meter and over wiper D2 in normal position to the private normal conductor extending to the final selector bank. so as'to busy the line against incoming calls. Relay'K is short-circuited at this time over contacts L2 and K2 and wiper D3. The magnet now operates and opens its interrupter contacts whereupon it releases and advances the Wipers into engagement with the first outgoing line. If. this line is busy, wiper D3 encounters earth and the driving circuit andvalso the shortclrcuit on relayK are maintained. When a free line is reached, wiper D3 fails to encounter earth and relay K operates in series with magnet DM which cannot now energise. Relay K at contacts KI disconnects relay L and connects up the negative wiper D5, at contacts K3 connects up the positive wiper D4, at contacts K2 prepares alocking circuit for itself to the P conductor and. at contacts K4 opens another point in the circuitof relay L and provides the operating earthfor the meter which it will be noted is now short-circuited. Relay L is made-sufficiently slow to release to cover-the time required for earthto be fed back over the P conductor from. the. seized first numerical switch so as to maintain relay K and the guard on the private normalconductor. It will be noted that as soon as the. switch steps off-normal the direct earth initially provided on this latter conductor is replaced by earth through the winding of relay Kwhich is accordingly of sufliciently low resistance to make this guarding effective.

,Whenthe connection isfully set up and the calledparty; replies, metering iseffected'by the connection of'booster battery to the P lead in well-known manner whereupon the meter MTR- operates to register the call. The-rectifier MRA is provided to obviate any tendency for the meter to remain operated in series with relay K when the connection is released.

When the calling party hangs up at the end of the conversation, the holding earth which has been supplied to the P conductor from the final selector or outgoing repeater is removed and relay K falls away. A homing circuit is then completed over contacts K4 and L2 and wiper DI and the uni-selector steps on to its normal position. I

On an incomin call earth is applied to the normal conductor extending from the final selector multiple FSM through both windings of a double-wound switching relay in the final selector. If the line is idle, this earth extends over wiper D2 in normal position, winding of relay K, resistance KYA, interrupter contacts DMC and winding of magnet DM to battery. The switching relay in the final selector thereupon operates and short-circuits one of its windings'so as to apply low resistance earth to the P conductor to guard the line and also to operate relay K which thereupon disconnects relay L in order to prevent its operation when the called party removes his receiver. When the connection is subsequently released, earth is removed from the P conductor and relay K restores to normal.

If a toll call arrives for the subscriber at a time when he is busy, the operator may efiect connection with the line circuit over her toll breakdown final selector and then converse with the party and inform him that a toll call is waiting. If she then institutes toll breakdown conditions, full earth is applied to the P conductor.

Considering first the case in which the party desired is the calling party in the established connection, his uniselector will be off-normal and the breakdown earth on the P conductor will therefore short-circuit relay K and cause its release but will not operate the magnet DM owing to the presence of the resistance KYA in the circuit. The release of relay K opens the loop forward so as to release the existing connection and since relay L is de-energized at. this time a homing circuit is completed for the uniselector. When the switch reaches normal position, circuits are completed for both relays K and L but since relay L is provided with a'small armature end slug, relay K operates first and opens the circuit of relay L. Relay K then performs its normal functions on an incoming call.

If the wanted party is the called subscriber in the existing connection, the toll breakdown earth will maintain the already operated relay K and will force down the switching relay in the final selector of the train already set up.

It may be mentioned that a toll tone is usually provided on toll calls so as to notify the operator and warn her not to break down an existing toll connection. This tone is connected to the P conductor and in order to secure that it shall pass satisfactorily, it may be desirable to shunt relay K with a condenser of suitable size.

As previously mentioned, alternative facilities are provided for connection of the common lead ill either direct to battery by way of the jumper represented by lines and circles or to battery via the key LDK by way of the jumper represented by lines and crosses. It will be appreciated'that if the key LDK is operated the subscribers concerned will be unable to make outgoing calls as their line relays cannot then be operated. The purpose of the arrangement is to permit the cutting off of subscribers not entitled to priority service so that priority subscribers will be able to make calls even if the exchange should become temporarily overloaded during emergency conditions.

It will be understood that the circuit for the line relay over a wiper of the uniselector, which prevents operation of the relay until the switch reaches the home position, could alternatively be included in the battery leg rather than the earth leg. This arrangement would have the possible advantage that in the event of an earth fault on the positive speaking wire, which would not necessarily put the line out of action, the line relay would till be prevented from operating until the switch reached normal position which would not be the case with the circuit shown.

In order to render the line circuit suitable for operation over long lines, it is desirable to have as much winding space as possible on the L rc" lay and if standard components are to be used this means reducing the size of the slug ordinarily employed to give this relay its slow releasing characteristic. As a result the lag on. the relay will be reduced but this may be safely done if arrangements are provided whereby the holding earth is fed back from the first selector switch with the least possible delay. This is effected by the modified selector switch shown in Figs. 2 and 3 which is arranged so that earth is fed back on the operation of relay A and is subsequently reinforced by earth provided by the so-called guard or release relay B. The switch of Figs. 2 and 3 is otherwise similar that shown in our Patent No. 2,137,423 granted November 22, 1938, and its operation will now be traced through briefly.

When the selector switches through, relay A operates over the loop by way of its upper and lower windings and applies an immediate earth to the P conductor over contacts C5, N2, Al and N4. Relay A also at these same contacts Al energises relay B in series with vertical magnet VM and resistance YA. Relay B thereupon completes a locking circuit for itself at contacts Bl, energises relay C by way of its upper winding at contacts B2, and reinforces the earth on the P conductor at contacts B3. Relay B also at contacts B4 completes a circuit for the supervisory lamp LP over common lead 25 which extends to delayed alarm equipment, at contacts B5 prepares circuits for relays HA and HB, at contacts B6 connects up dial tone from common lead 23 to the middle winding of relay A whence it is transmitted by induction to the line windings and at contacts B! opens a point in the release circuit. Relay C at contacts Cl prepares a circuit for its lower winding, at contacts C2 closes another point in the circuit for relays HA and HB, at contacts C3 and C6 closes points in the speaking leads, at contacts C5 opens the initial circuit for relay B and at contacts C4 opens a point in the circuit of the rotary magnet RM.

The switch is now in a condition to respond to dialled impulses nd when these are transmitted relay A operates accordingly. On the first release of relay A, a circuit is completed for the vertical magnet VM by way of contacts Bl, Al, NR4, Cl, lower winding of relay C, winding of vertical magnet VM to battery. The switch wipers are therefore raised one step and the 01?- normal contacts are operated whereupon at contacts NI relays HA and HB are operated over their middle windings. Thereupon, at contacts seized. Moreover, at contacts HA! and HB2 theycomplete a locking circuit'fo'r themselves While at contacts HA3 and HBB the upper winding of relay C is short-circuite'd. This relay, however, continues to hold up throughout the train of impulses due to the intermittent energisation of its lower winding in series with magnet VM.

On the termination of the impulse train, relay C releases and at contacts C4 completes a circuit for the rotary magnet. This accordingly advances the wipers into engagement with the first set of contacts and the normal rotary contacts are open operated. Moreover, when the rotary magnet completes its stroke the interrupter contacts RMC are opened, thereby interrupting the circuit 'for the magnet and also the initial circuit for relays HA and HB. If, however, both the lines now engaged by the two sets of wipers are busy, wiper PI and P2 will both encounter earth and relays HA and HB will be maintained 'over their right-hand windings. Accordingly, when contacts RMC again close on the de-energisation of the rotary magnet, a further energising circuit is completed and the wipers are advanced afurther step. This continues until an idle line is found or the wipers are driven to the overflow position.

If the upper set of wipers encounters a tree line and the lower set a busy line, relay I-IB releases owing to the failure of wiper Pl tofind earth and at contacts HB5 applies immediate guarding earth from contact B3 to busy the line HB6 the short-circuit is removed from relay C which therefore now operates and a holding circuit is completed for relay HA from earth, contacts B3, I-IB2, left-hand winding of relay HA, contact NR4, 'Cl, lower winding of relay C, winding of vertical magnet VM to battery. At contacts C3 and C6 the speaking leads are switched through in conjunction with contacts HA2 and HA6 and the former contacts also disconnect relay A which now releases and short-circuits relay B which also releases after a slight interval. Earth is now fed back over wiper Pl from the succeeding switch to maintain relay HA and also relay K in the subscribers line circuit while relay C is maintained over contacts HAT.

If on the other hand the upper set of wipers'engages a busy line and the lower stia free line, relay HA de-energises and at contact HA5 provides an immediate guard for the seized line. Contacts HBS and HA3 in this case provide the circuit for relay C and relay HE is held up over its left-hand winding by way of contaotsI-IBZ and HA! and the circuit to battery through relay C and magnet VlVi as previously traced.

If both sets of wipers encounter free lines, relays HA and HE both de-energise and guarding earth is applied to wiper Pl over contacts B4. In these circumstances, on the re-operation of relay C over contacts B2, a circuit is completed for relay HA as previously traced but no circuit is completed for relay HB so that the upper set of wipers has preference.

If all the lines in the selected level are busy, the wipers advance to the 11th position in which the S contacts are operated. Thereupon at contacts S2 earth is extended over wiper Pl to lead 26 which is connected to an overflow meter, at contacts Si busy tone over lead 22 is connected up in place of dial tone and at contacts S3 busy flash in the form of alternate battery and earth connections is connected to the middle and lower windings of relay A to give the necessary signal in case the call has been setup by an operator.

When release is to take place at the end of the connection, earth is removed from the P conductor to permit the release of relay HA or I-IB as the case may be. Relay C is also then released and a circuit for the rotary magnet is completed by way of contacts C4, Ni, RMC, C2, BI and link T to common lead 24 which extends to earth by way of release alarm equipment. The wipers are then advanced to 12th position in which they move clear of the bank, fall and rotate to normal underneath it in well-known manner.

It is important for the purpose of securing an immediate holding earth that relay A should operate'as rapidly as possible. This relay however maybe energised over a very long line and there fore its spring load must be reduced as far as possible. It will be seen that relay A still has only one spring combination which is used for operating relay B and subsequently repeating impulses and the additional holding function is also performed by this spring combination.

The invention therefore provides an improved linewcircuit which gives additional facilities with out increasing the amount of equipment required while at the same time there is no sacrifice of reliability of operation.

We claim:

, 1 In a telephone or like system, a subscribers line circuit comprising a .cut-ofi relay and a nonnumerical switch of the rotary homing type giving access'to a group or first numerical switches, a wiper on said switch, a guard lead for said circuit connected to said wiper, means including said wiper and'a potential connected directly to said guard lead for operating said cut-off relay in case said rotary switch is connected to one of said numerical switches, means responsive to the operation of said cut-off relay for restoring saidrotary switch to its home position, and means including said wiper and said potential for fur-- ther operating said out off relay after said rotary switch has reached its home position to maintain said rotary switch therein.

2. In a telephone or like system, a subscribers line, a line circuit therefor comprising a cut-off relay and a rotary switch, a group of trunk circuits accessible to said rotary switch, a wiper on said rotary switch having a guard lead for sai line circuit connected thereto, means for operating said cut-off relay in response to the connection'oi said rotary switch to one of said trunk circuits to connect said line thereto and to extend a guarding potential to said guard lead through the winding of said cut-off relay and said wiper, means for releasing saidcut-ofi relay in. response to the connection of a similar potential directly '-'to said guard lead to disconnect said line from said trunk circuit.

3. Ina telephone or like system, a subsoribers line, a line circuit therefor comprising a relay and a rotary switch having a normal position, a group "of automatic switches accessible to said rotary switch, a wiper on said rotary switch having a guard lead for said-line circuit connected thereto,

means for operating said relay in response to the connection of said rotary switch to one of said automatic switches to connect said line thereto and to extendaguarding potential to said guard lead through the winding of said relay and said wiper, means for releasing said relay in response to the connection of a similar potential directly to said guard lead to disconnect said line from said automatic switch, means responsive to the release of said relay for restoring said rotary switch to its normal position, and means effective thereafter for operating said relay tomaintain said rotary switch in its normal position, said last means including said similar potential and said wiper.

4. In a telephone or like system, a rotary switch having a home position, a wiper on said switch, a guard lead connected to said wiper, one contact engaged by said wiper with said switch in its home position, other contacts for engagement by said wiper in case said switch is moved from its home position, a relay, means including said wiper and said one contact for operating said relay in one manner from a. potential applied to said guard lead with said switch in its home position, and means including said wiper and one of said other contacts for operating said relay in another manner from a similar potential applied to said guard lead in case said switch is 01f normal.

5. In a telephone or like system, a rotary switch having a normal position, wipers on said switch, normal contacts engaged by said wipers with said switch in its normal position, other contacts engaged by said wipers with said switch off normal, a, line relay having a starting circuit including one of said wipers and one of said normal contacts, a cut-off relay having a starting circuit including another of said wipers and another of said normal contacts whereby said starting circuits are disabled in case said switch is oiT normal, a group of automatic switches, means including said line relay for establishing a connection between said rotary switch and one of said automatic switches, means for operating said cut-off relay in response to said connection, means including said other wiper and one of said other contacts for releasing said cut-off relay, means for releasing said connection and for restoring said rotary switch to its normal position in response to the release of said cut-ofi relay, said wipers being effective to prevent the closure of said starting circuits while said rotary switch is ofi" normal.

6. A telephone or like system as set forth in claim 5 in which said cut-01f relay operates thereby preventing the operation of said line relay in case both of said starting circuits are closed at the same time.

7. A telephone or like system as set forth in claim 5 in which said one wiper included in the starting circuit for the line relay is also included in the means for restoring said rotary switch to its normal position.

8. In a telephone or like system, a subscribers line, a line circuit comprising a line relay and a cut-01f relay and a non-numerical switch of the rotary homing type giving access to a group of numerical switches, means including said switch for establishing a, connection between said line and one of said numerical switches, said cut-off relay being operated and said non-numerical switch being in a non-home position during said connection, a relay in said numerical switch operated over said line immediately said connection is established to connect a holding circuit to said cut-off relay, a guard lead for said line circuit, means including said guard lead responsive to the extension of another connection to the line for releasing said cut-01f relay in case said line is connected to one of said numerical switches, to thereby disable said connection to the numerical switch.

9. In a telephone system, a subscribers line, a line circuit therefor comprising a line relay and a cut-off relay and a rotary switch having a normal position, said line relay being operative responsive to the closure of said line, a group f trunk circuits, means responsive to the operation of said line relay for operating said switch to seize one of said trunk circuits, said cut-oif relay operated thereafter under control of said line relay to disable same and to connect said line to said one trunk circuit, a relay in said one trunk circuit operated in series with said line to connect a potential to said cut-01f relay to hold it operated, slow release means in said line relay whereby it remains operated to hold said cutofi relay until said potential is connected thereto, a wiper on said switch, a guard lead connected to said wiper, means for connecting said potential, through the winding of said cut-01f relay and said wiper to said guard lead thereby making it a guarding potential for said line circuit, means responsive to the connection of a similar potential directly to said guard lead for releasing said cut-off relay to release said one trunk circuit and to disconnect said line therefrom, means responsive to the release of said cut-01f relay for restoring said switch to its normal position, and means effective thereafter and including said wiper and said potential connected directly to said guard lead for operating said cut-01f relay to maintain said switch in. its normal position.

10. In a telephone or like system, a subscribers line, a line circuit comprising a line relay and a cut-off relay and a rotary switch having a normal position, a group of automatic switches, a key having normally closed contacts, an operating power source connected to said line relay through said contacts, in case said key is normal said line relay being operative in response to the initiation of a call on said line to control the connection of said rotary switch and said line to .one of said automatic switches, in case said key is operated said line relay being inoperative to thereby disable said line for the extension of outgoing calls, a wiper on said rotary switch, a guard lead connected to said wiper, means including said wiper and said cut-01f relay and effective in case a connection is established between said line and one of said automatic switches for releasing said connection in response to the connection of ground directly to said guard lead.

REGINALD TAYLOR. GEORGE THOMAS BAKER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,669,031 Willis May 8, 1928 1,718,976 Ostline June 2, 1929 1,757,681 Ostline May 6, 1930 

